KR20200055602A - Sensor pixel, fingerprint and image sensor, and driving method thereof - Google Patents

Abstract

The present invention relates to a sensor pixel capable of adjusting an exposure time, a fingerprint and image sensor including the same, and a driving method thereof. The fingerprint and image sensor comprises: a plurality of data lines; a plurality of scan lines through which a plurality of scan signals are transmitted; and a sensor panel including a plurality of sensor pixels that are reset by a plurality of reset scan lines to which a plurality of reset scan signals are transmitted, and a reset voltage transmitted in synchronization with a corresponding reset scan signal, generates a pixel voltage according to light supplied during an exposure period, and transmits the pixel voltage to a corresponding data line in synchronization with a corresponding scan signal, wherein the exposure period may be a period from a time when the corresponding reset scan signal is changed to an off-level to a time when the corresponding scan signal is changed to an on-level.

Description

A sensor pixel, a fingerprint and image sensor including the same, and a driving method thereof {SENSOR PIXEL, FINGERPRINT AND IMAGE SENSOR, AND DRIVING METHOD THEREOF}

The present disclosure relates to an optical sensor pixel, a fingerprint and image sensor including the same, and a driving method thereof.

Since the optical fingerprint and image sensor recognizes an object based on the amount of light received by the sensor, it is affected by the amount of light in the place where the sensor is located. When the fingerprint and image sensor operate in an environment with a large amount of light, there is a problem that it is difficult to accurately recognize an object due to the influence of ambient light.

In order to solve this problem, circuits (global shutter, rolling shutter, etc.) that electrically block a signal when there is a large amount of light using a shutter in a pixel have been developed. However, there is a problem in that image distortion is caused by blocking circuits using a shutter, and the driving speed of the fingerprint and the image sensor is limited.

It is intended to solve the problem of not recognizing fingerprints and images due to the influence of the amount of light in the surrounding environment, and to provide a sensor pixel having an unlimited driving speed, a fingerprint and image sensor including the same, and a driving method thereof.

Fingerprint and image sensor according to one aspect of the invention, a plurality of data lines, a plurality of scan lines through which a plurality of scan signals are transmitted, a plurality of reset scan lines through which a plurality of reset scan signals are transmitted, and a corresponding reset scan signal It is reset by a reset voltage transmitted in synchronization, and generates a pixel voltage according to the light supplied during the exposure period, and includes a plurality of sensor pixels transmitting the pixel voltage to a corresponding data line in synchronization with a corresponding scan signal. It includes a sensor panel. The exposure period may be a period from a time when the corresponding reset scan signal is changed to an off level to a time when the corresponding scan signal is changed to an on level.

The corresponding reset scan signal may have a predetermined phase difference in the same waveform as the corresponding scan signal.

The corresponding reset scan signal has an on level at least twice in one frame period, and the exposure period corresponds to the corresponding reset scan signal from a point in time when the corresponding reset scan signal is changed from one on level to an off level. It may be a period until the time when the scan signal is changed to the on level.

The corresponding reset scan signal may have an on level periodically after a point in time during which the corresponding scan signal is changed from an on level to an off level during the one frame period.

The corresponding reset scan signal is off level for a predetermined period of one frame period, and in the exposure period, the corresponding scan signal is changed to an on level from a time when the corresponding reset scan signal is changed from an on level to an off level. It can be a period up to the point in time.

The sensor pixel according to another aspect of the invention generates a pixel voltage according to the supplied light, resets a photodiode connected between a first contact and a bias voltage, a capacitive capacitor connected in parallel to the photodiode, and a reset voltage And a reset transistor that supplies the first contact according to the scan signal, and a switching transistor that delivers the pixel voltage, which is the voltage of the first contact, to the data line according to the scan signal. Signals may be accumulated in the capacitor during an exposure period from a time when the reset scan signal is changed to an off level to a time when the scan signal is changed to an on level.

The corresponding reset scan signal may have a predetermined phase difference in the same waveform as the corresponding scan signal.

The corresponding reset scan signal has an on level at least twice in one frame period, and the exposure period corresponds to the corresponding reset scan signal from a point in time when the corresponding reset scan signal is changed from one on level to an off level. It may be a period until the time when the scan signal is changed to the on level.

The corresponding reset scan signal may have an on level periodically after a point in time during which the corresponding scan signal is changed from an on level to an off level during the one frame period.

The corresponding reset scan signal is off level for a predetermined period of one frame period, and in the exposure period, the corresponding scan signal is changed to an on level from a time when the corresponding reset scan signal is changed from an on level to an off level. It can be a period up to the point in time.

According to another aspect of the present invention, a method of driving a fingerprint and image sensor including a plurality of sensor pixels includes transmitting a plurality of reset scan signals to each of the plurality of sensor pixels, and scanning a plurality of each of the plurality of sensor pixels. During the exposure period from the time of transmitting a signal and the time when each of the plurality of reset scan signals is changed to an off level to a time when each of the plurality of scan signals is changed to an on level, light is supplied to the plurality of sensor pixels. Accordingly, the method includes generating a plurality of pixel voltages, and transferring the plurality of pixel voltages to a plurality of data lines in synchronization with on-levels of each of the plurality of scan signals.

Each of the plurality of reset scan signals may have a predetermined phase difference in the same waveform as a corresponding scan signal among the plurality of scan signals.

Each of the plurality of reset scan signals has an on level at least twice during one frame period, and the exposure period is a time point at which each of the plurality of reset scan signals changes from one on level to at least two off levels. It may be a period from to the time point when the scan signal is changed to the on level.

Each of the plurality of reset scan signals may have an on level periodically after a point in time during which the corresponding scan signal among the plurality of scan signals is changed from an on level to an off level during the one frame period.

Each of the plurality of reset scan signals is off level for a predetermined period of one frame period, and in the exposure period, the scan signal is changed to an on level from the time each of the plurality of reset scan signals is changed from an on level to an off level. It can be a period up to the point in time.

Provided is a sensor pixel capable of adjusting exposure time, a fingerprint and image sensor including the same, and a driving method thereof.

1 is a view showing the configuration of a fingerprint and an image sensor according to an embodiment.
2 is a diagram illustrating a part of a plurality of sensor pixels, a multiplexing circuit, and an amplifying circuit according to an embodiment.
3 is a waveform diagram showing a scan signal.
4 is a waveform diagram showing a switching signal and a reset signal.
5 is a waveform diagram showing a pixel voltage according to a change in a reset voltage according to the amount of light.
6 is a graph showing the relationship between the luminance and gradation values of a fingerprint and an image sensor according to a change in reset voltage according to an embodiment.
7 is a diagram illustrating a waveform of a reset scan signal according to another embodiment.
8 is a diagram illustrating a waveform of a reset scan signal according to another embodiment.
9 is a view showing a waveform of a reset scan signal according to another embodiment.

The fingerprint and image sensor according to the embodiment can be used without being influenced by the amount of light in the surrounding environment by adapting to the environment according to changes in light. To this end, the operating areas of the fingerprint and image sensor may be adjusted according to the light intensity. A pixel reset voltage that changes the operating area of the sensor according to the amount of light may be applied to the fingerprint and image sensors. Specifically, the pixel reset voltage is changed according to the amount of light to adjust the range of the pixel voltage corresponding to the detected amount of light, and the voltage difference between the reference voltage and the pixel voltage for signal processing is adjusted to shift the operating area of the fingerprint and image sensor do.

Hereinafter, embodiments will be described in detail with reference to the drawings.

1 is a view showing the configuration of a fingerprint and an image sensor according to an embodiment.

As shown in FIG. 1, the sensor 1 includes a sensor panel 10, a gate driving circuit 20, a sensing readout circuit 30, a reset voltage generation circuit 40, a light sensing circuit 50, and a bias voltage. It includes a generation circuit 60, and a light source (70).

The sensor panel 10 has a plurality of gate lines S1-S11, a plurality of reset gate lines SR1-SR11, a plurality of data lines D1-D16, and reset voltage lines RE, RE1-RE16. do. Although not shown in FIG. 1, a line to which the bias voltage VB is supplied may also be located on the sensor panel 10. In FIG. 1, the sensor panel 10 is illustrated as having a size of 16X11, but the invention is not limited thereto.

The plurality of gate lines S1-S11 extend in a first direction (horizontal direction in FIG. 1) and are arranged along a second direction (vertical direction in FIG. 1) intersecting the first direction. A scan signal corresponding to each of the plurality of sensor pixel rows is transmitted through the plurality of gate lines S1-S11.

The plurality of reset gate lines SR1-SR11 extend in the first direction (horizontal direction in FIG. 1), are arranged along the second direction, and are positioned parallel to the corresponding gate line. A reset scan signal corresponding to each of the plurality of sensor pixel rows is transmitted through the plurality of reset gate lines SR1-SR11.

The plurality of data lines D1-D16 extend in the second direction and are arranged in the first direction. The pixel voltage of each of the plurality of sensor pixels is transmitted to the sensing readout circuit 30 through the plurality of data lines D1-D16.

Each of the plurality of sensor pixels PX is connected to a corresponding gate line, a reset gate line, and a data line, the pixel voltage is reset in synchronization with a reset scan signal transmitted through the corresponding reset gate line, and the corresponding gate The pixel voltage may be transferred to the corresponding data line in synchronization with the scan signal transmitted through the line.

A reset voltage line RE1 extending in a first direction and reset voltage lines RE1-RE16 extending in a second direction from the reset voltage line RE and corresponding to a plurality of sensor pixel columns may be located on the sensor panel 10. Can be. The reset voltage lines RE and RE1-RE16 shown in FIG. 1 are examples and the invention is not limited thereto.

The gate driving circuit 20 may sequentially generate a plurality of scan signals and supply them to the plurality of gate lines S1-S11, and generate a plurality of reset scan signals and supply them to the plurality of reset gate lines SR1-SR11. have.

In one embodiment, all of the sensor pixels PX on the sensor panel 10 are reset to the reset voltage VRS in synchronization with the on-level reset scan signal, and a plurality of scans of the on-level sequentially in a plurality of sensor pixel rows Signals can be supplied.

The sensing readout circuit 30 amplifies the voltage difference between each of the plurality of pixel voltages supplied from the plurality of data lines D1-D16 and the reference voltage to generate a plurality of output voltages, and the fingerprint sensed according to the plurality of output voltages Alternatively, an image may be generated as a video signal.

The sensing read circuit 30 includes a multiplexing circuit 31, an amplifying circuit 32, and a signal processing circuit 33.

The multiplexing circuit 31 may generate a plurality of data voltages VD1-VD4 by multiplexing a plurality of pixel voltages supplied through the plurality of data lines D1-D16 at a 4: 1 ratio. In the embodiment, the multiplexing circuit 31 is implemented in 4: 1 MUX, but the invention is not limited to this as an example. The multiplexing circuit 31 includes a plurality of switches, one end of which is connected to each of the plurality of data lines D1-D16. The plurality of switches may be grouped in four units to form one channel. In FIG. 1, since the number of data lines is 16, four channels are formed through a 4: 1 MUX. The data voltages VD1-VD4 are transmitted to the amplifying circuit 32 through each of the four channels.

The amplifying circuit 32 amplifies the voltage difference between each of the data voltages VD1-VD4 and the reference voltage to generate the output voltage VO1-VO4 and transmits it to the signal processing circuit 33.

The signal processing circuit 33 may generate an image signal representing a sensed fingerprint or image based on addresses corresponding to each of the output voltages VO1-VO4 and VO1-VO4.

The signal processing circuit 33 may generate a switching signal MS1-MS4 that controls the switches of the multiplexing circuit 31 and a reset signal AS1-AS4 that resets the output of the amplifying circuit 32. . Since the signal processing circuit 33 can know the position of the sensor pixel row to which the scan signal of the on-level is transmitted at the time when each of the plurality of scan signals is turned on, and controls the switching operation of the multiplexing circuit 31 The position of the sensor pixel row input through each channel can be known. Therefore, the address of the sensor pixel corresponding to the output voltage VO1-VO4 supplied from the amplifying circuit 32 can be known.

In the case of optical fingerprint recognition, the signal processing circuit 33 may generate an image signal representing a sensed fingerprint or image based on addresses corresponding to each of the output voltages VO1-VO4 and VO1-VO4. .

 The photo sensing circuit 50 detects the amount of light in the environment where the fingerprint and image sensor 1 are located and transmits the photo sensing signal LS indicating the information about the amount of light to the reset voltage generation circuit 40.

The reset voltage generation circuit 40 determines the level of the reset voltage VRS based on the light detection signal LS, generates the reset voltage VRS and supplies it to the reset voltage line RE. For example, the reset voltage generation circuit 40 may increase the reset voltage VRS as the amount of light increases, and decrease the reset voltage VRS as the amount of light decreases. However, in this case, the reset voltage VRS may be reduced to a reference voltage.

The bias voltage generation circuit 60 generates a bias voltage VB and supplies it to the sensor panel 10, and a bias voltage VB is supplied to each of the plurality of sensor pixels PX through a bias voltage line.

The light source 70 provides light necessary for optical fingerprinting and image sensing. The light source 70 is located at the rear of the sensor panel 10 to provide light to the front.

2 is a view showing a part of a plurality of sensor pixels, a multiplexing circuit, and an amplifying circuit according to an embodiment.

In FIG. 2, four sensor pixels PX1-PX4 of the first sensor pixel row, four switches M1-M4 connected to four data lines D1-D4 in the multiplexing circuit 31, and an amplifying circuit 32 ), One operational amplifier 321 connected to a channel corresponding to four data lines D1-D4 is illustrated. Those skilled in the art to which the present invention pertains may know the overall configuration based on some configurations shown in FIG. 2.

Each of the sensor pixels PX1-PX4 has a corresponding data line (one of D1-D4), a corresponding reset voltage line (one of RE1-RE4), a corresponding bias voltage line (one of VB1-VB4), and a gate line ( S1), and the reset gate line SR1.

Each of the sensor pixels PX1-PX4 is a switching transistor T2, T4, T6, T8 switched by the scan signal S [1], and a reset transistor T1, T3, switched by the reset scan signal SR. T5, T7), photodiodes PD1-PD4, and capacitors C1-C4. Since the connection relationship between the switching transistor, the reset transistor, the photodiode, and the capacitor in each of the sensor pixels PX1-PX4 is the same, only the sensor pixel PX1 will be described.

The reset transistor T1 includes a gate electrode connected to the reset gate line SR1, one electrode connected to the reset voltage line RE1, and another electrode connected to the contact NP. The switching transistor T2 includes a gate electrode connected to the gate line S1, one electrode connected to the data line D1, and another electrode connected to the contact NP. The photodiode PD1 includes an anode electrode connected to the bias voltage line VB1 and a cathode electrode connected to the contact NP. The capacitor C1 includes one electrode connected to the bias voltage line VB1 and the other electrode connected to the contact NP. Hereinafter, the voltage of the contact NP is referred to as a pixel voltage VPX.

A capacitance is formed between each of the data lines D1-D4 and another adjacent electrode (not shown), and the capacitance is illustrated in FIG. 2 as the data line capacitors DCP1-DCP4. The data line capacitor DCP1-DCP4 is electrically connected to the data lines D1-D4.

In the multiplexing circuit 31, the switch M1 includes one electrode connected to the data line D1, another electrode connected to the channel CH1, and a gate electrode to which the switching signal MS1 is supplied, The switch M2 includes one electrode connected to the data line D2, another electrode connected to the channel CH1, and a gate electrode to which the switching signal MS2 is supplied, and the switch M3 includes the data line It includes one electrode connected to (D3), another electrode connected to the channel (CH1), and a gate electrode to which the switching signal (MS3) is supplied, and the switch (M4) is connected to the data line (D4). It includes one electrode, another electrode connected to the channel CH1, and a gate electrode to which the switching signal MS4 is supplied.

In the amplifying circuit 32, the operational amplifier 321 includes a non-inverting terminal (+) to which the reference voltage VRE is input, an inverting terminal (-) to which the data voltage VD1 is input through the channel CH1, and an output. It includes an output terminal through which the voltage VO1 is output. The feedback capacitor CA1 is connected between the inverting terminal (-) of the operational amplifier 321 and the output terminal, and the reset switch SW1 is connected in parallel to the feedback capacitor CA1. The reset switch SW1 may be switched by the reset signal AS1.

When the reset switch SW1 of the operational amplifier 321 is turned on, the channel CH1 between the switches M1, M2, M3, and M4 and the operational amplifier 321 and the output value of the operational amplifier 321 are the reference voltage ( VRE). After the reset, in the channel CH1, during the on period of the switch M1, current flows from the sensor pixel PX1, and the flowed current is integrated by the capacitor CA1 of the operational amplifier 321. Then, the output voltage VO1 is generated as a voltage based on the integration result in the capacitor CA1. At this time, the capacity of the capacitor CA1 and the output voltage VO1 are inversely related. Therefore, even if the amount of charge flowing into the channel CH1 from the sensor pixel PX1 is the same, the output voltage VO1 decreases as the capacity of the capacitor CA1 increases, and the output voltage VO1 decreases as the capacity of the capacitor CA1 decreases. Increases.

Hereinafter, the operation of the fingerprint and image sensor according to the embodiment will be described with reference to FIGS. 3 and 4.

3 is a waveform diagram showing a scan signal. 4 is a waveform diagram showing a switching signal and a reset signal.

The plurality of reset scan signals SR1-SRn may be changed from an on level to an off level before the on level of the corresponding scan signal. Detailed description thereof will be described later. When the plurality of reset scan signals SR [1] -SR [11] are at a high level, which is an on level, reset transistors of all sensor pixels PX are turned on. Then, the pixel voltage VPX of all sensor pixels PX becomes a reset voltage.

Next, scan signals S [1] -S [11] having an on level are sequentially supplied from the gate line S1 to the gate line S11. For example, the scan signal S [1] becomes a high level that is on level for a period P1 from time T1, and then the scan signal S [2] is a high level that is on level for a period P2 from a time T2. The scan signal S [11] becomes a high level, which is an on level from the time point T3 to a period P3. The on-level periods of each of the scan signals S [1] -S [11]) may be the same.

After the reset scan signal is turned off, the light supplied from the light source 70 is reflected to the recognition object and can be recognized by the sensor pixel PX. For example, when recognizing a fingerprint, in the case of a ridge of a fingerprint, the amount of light reflected from the light source 70 to the sensor pixel PX is high due to the ridge of the fingerprint being in close contact with the sensor panel 1, and In the case of a valley, the amount of light reflected from the light source 70 to the sensor pixel PX by the space between the valley of the fingerprint and the sensor panel 1 is relatively small.

A current flows through the photodiode (PD1-PD4 in FIG. 2) according to the amount of light incident on each of the sensor pixels PX. At this time, the direction of the current flowing through the photodiode is from the cathode to the anode, and the charge of the capacitor (C1-C4 in FIG. 2) is discharged by the current flowing through the photodiode. Then, the discharge level of the capacitor is changed according to the amount of light incident on each of the sensor pixels PX, and the pixel voltage VPX is determined according to the amount of light. For example, as the amount of light increases, the pixel voltage VPX may decrease.

During the on-level period of each of the scan signals S [1] -S [11], the pixel voltage (VPX1-VPX4 in FIG. 2) is transmitted to the multiplexing circuit 31 through the data lines D1-D16, and the multiplexing circuit The pixel voltages transferred from the corresponding data lines (31) are multiplexed and output as the data voltages VD1-VD4. At this time, the data line capacitor (DCP1-DCP4 in FIG. 2) may maintain the pixel voltage transmitted through the data line.

As shown in FIG. 4, during the on-level period P1 of the scan signal S [1], the switching signals MS1-MS4 may be sequentially turned on, a high level.

First, in periods T9-T10, during period P4, the reset signal AS1 becomes a high level that is an on level and the reset switch SW1 is turned on, so that the output voltage VO1 may be reset to the reference voltage VRE.

During periods T11-T12, the switching signal MS1 is at a high level so that the switch M1 is turned on, current flows from the sensor pixel PX1 through the data line D1, and the flowed current is an operational amplifier ( Integrated by capacitor CA1 of 321, output voltage VO1 is generated. During periods T13-T14, the switching signal MS2 is at a high level, the switch M2 is turned on, current flows from the sensor pixel PX2 through the data line D2, and the flowed current is an operational amplifier ( Integrated by capacitor CA1 of 321, output voltage VO1 is generated. During periods T15-T16, the switching signal MS3 is at a high level so that the switch M3 is turned on, current flows from the sensor pixel PX3 through the data line D3, and the flowed current is an operational amplifier ( Integrated by capacitor CA1 of 321, output voltage VO1 is generated. During periods T17-T18, the switching signal MS4 is at a high level and the switch M4 is turned on, current flows from the sensor pixel PX4 through the data line D4, and the flowed current is the operational amplifier ( Integrated by capacitor CA1 of 321, output voltage VO1 is generated.

In periods T12-T13, periods T14-T15, and periods T16-T17, respectively, during period P4, the reset signal AS1 becomes the high level, which is the on level, and the reset switch SW1 is turned on, so that the output voltage VO1 is turned on. It may be reset to the reference voltage VRE. The on-level period of the reset signal AS1 may be constant as the period P4.

5 is a waveform diagram showing a pixel voltage according to a change in a reset voltage according to the amount of light.

In FIG. 5, the pixel voltage VPX1 of the sensor pixel PX1 is illustrated. Since pixel voltages of other pixel circuits may also have the same waveform, a description thereof is omitted.

As shown in FIG. 5, the reset voltage generation circuit 40 may set the reset voltage VRS based on the light sensing signal LS.

For example, when the light detection signal LS indicates a predetermined threshold light level or less, the reset voltage generation circuit 40 may set the reset voltage VRS as the reference voltage VRE.

Then, the pixel voltage (for example, VPX1) is maintained as the reset voltage VRS before the time point T31, and when light is supplied from the light source 70 after the time point T31, the pixel is caused by the current flowing through the photodiode PD1. The voltage VPX1 can be determined. The pixel voltage VPX1 decreases as the amount of light reflected by the sensor pixel (eg, PX1) increases.

When the switching transistor T2 and the switch M1 are turned on after the time point T31, current flows from the sensor pixel PX1, and the flowed current is integrated by the capacitor CA1 of the operational amplifier 321, The output voltage VO1 is generated. When the data voltage VD1 is greater than the reference voltage VRE, the output voltage VO1 is saturated with the power supply voltage of the operational amplifier 321, so that the output voltage VO1 according to the data voltage VD1 is not generated. Therefore, the output voltage VO1 may be generated after the time T31 when the data voltage VD1 decreases to the reference voltage VRE.

As another example, when the light detection signal LS indicates an arbitrary first level above a predetermined threshold amount of light, the reset voltage generation circuit 40 sets the reset voltage VRS to a reset voltage higher than the reference voltage VRE ( VRS1).

Then, as shown in FIG. 5, when the pixel voltage VPX1 is maintained as the reset voltage VRS1 before the time point T31, and light is supplied from the light source 70 after the time point T31, it flows through the photodiode PD1. The pixel voltage VPX1 may be determined by the current. The switching transistor T2 and the switch M1 are turned on after the time point T31 and the data voltage VD1 is reduced to the reference voltage VRE. The output voltage VO1 may be generated by being integrated by the capacitor CA1 of 321.

As another example, when the light detection signal LS indicates an arbitrary second level (> first level) equal to or greater than a predetermined threshold amount of light, the reset voltage generation circuit 40 sets the reset voltage VRS to the reset voltage ( VRS1) may be set to a higher reset voltage (VRS2).

Then, as illustrated in FIG. 5, when the pixel voltage VPX1 is maintained as the reset voltage VRS2 before the time point T31, and light is supplied from the light source 70 after the time point T31, it flows through the photodiode PD1. The pixel voltage VPX1 may be determined by the current. The switching transistor T2 and the switch M1 are turned on after the time point T31 and the data voltage VD1 decreases to the reference voltage VRE. The output voltage VO1 may be generated by being integrated by the capacitor CA1 of 321.

As illustrated in FIG. 5, as the light supplied to the sensor pixel PX1 increases, the pixel voltage VPX1 decreases and may decrease to the bias voltage VB.

6 is a graph showing the relationship between the luminance and gradation values of a fingerprint and an image sensor according to a change in reset voltage according to an embodiment.

As shown in FIG. 6, when the reset voltage VRS is varied to 0.5V, 1V, 1.5V, 2V, 2.5V, 3V, and 3.3V, the illumination-gradation curves are operated without changing the slope thereof. It can be seen that this shift. The illuminance is the illuminance of the light supplied to the sensor pixel, and the gradation value may mean an image signal generated based on the output voltage VO1-VO4 in the signal processing circuit 33.

The sensitivity of the fingerprint and image sensor 1 depends on the slope of the illuminance-gradation value curve. As can be seen in FIG. 6, it can be seen that only the operating region is shifted without changing the sensitivity.

When the value of the reset voltage VRS increases as the amount of light in the external environment increases, the operating area of the fingerprint and image sensor 1 can be increased as compared to the prior art.

For example, it is assumed that the illumination level of the external environment is 400 lux, and the external light amount is supplied to the sensor pixel PX1 as it is. In this case, when the reset voltage VRS is 0.5V, the operating region of the fingerprint and image sensor 1 is approximately in the range of 230 to 250 gradation values. As the reset voltage VRS is increased, the operation area of the fingerprint and image sensor 1 increases, and when the reset voltage VRS is 3.3V, the operation area is approximately 40 to 250 gradation value range.

As described above, according to the embodiment, by setting the reset voltage according to the amount of external light, an effect of securing an operating area without changing the sensitivity of the fingerprint and the image sensor may be provided.

7 is a diagram illustrating a waveform of a reset scan signal according to another embodiment.

As shown in Fig. 7, the reset scan signal SR [1] becomes a high level which is an on level during periods T51-T52. The scan signal S [1] corresponding to the reset scan signal SR [1] rises to a high level, which is an on level at time T55. Then, all sensor pixels of the corresponding sensor pixel row (eg, the first sensor pixel row) are exposed to light during the period PT1 (T52-T55). That is, the exposure time can be adjusted by adjusting the period from the falling edge of the reset scan signal SR [1] to the rising edge of the scan signal S [1].

Subsequently, the reset scan signal SR [2] becomes a high level, which is an on level during periods T53-T54. The scan signal S [2] corresponding to the reset scan signal SR [2] rises to a high level, which is an on level at time T56. Then, all sensor pixels of the corresponding sensor pixel row (for example, the second sensor pixel row) have an exposure time for the period PT2 (T54-T56).

In this way, a plurality of reset scan signals and a plurality of scan signals are generated.

When the reset scan signal SR [1] is turned on and the transistor T1 is turned on, the voltage of the node NP is reset. When the reset scan signal SR [1] goes off-level, a signal is accumulated in the capacitor C1 from this time. After the exposure time T52-T55, when the corresponding scan signal S [1] is turned on, the transistor T2 is turned on, and the signal accumulated in the capacitor C1 is transmitted to the data line. Then, when the scan signal goes off level at time T57, the signal starts to accumulate again in the capacitor C1, and when the reset scan signal SR [1] goes back to the on level, the voltage of the node NP is reset. , Signals accumulated during this period (eg T57-T58) are discarded.

As shown in FIG. 7, if the waveforms of the scan signal and the reset scan signal are similar, the circuit structure of the gate driving circuit for generating the reset scan signal may be the same as the circuit structure of the shift register for generating the scan signal. . In this way, the exposure time can be adjusted by using the phase difference between the scan signal and the reset scan signal.

8 is a diagram illustrating a waveform of a reset scan signal according to another embodiment.

8, the reset scan signal is turned on at least twice during one frame period.

For example, in the reset scan signal SR [1], the scan signal S [1] is turned on, and the signal accumulated in the capacitor C1 is transmitted to the data line, and then again for the periods T71 and T72. It becomes on level. In the reset scan signal SR [2], the scan signal S [2] is turned on, and after the signal accumulated in the capacitor C1 is transmitted to the data line, it is turned on again for the periods T73 and T74. .

In FIG. 8, the reset scan signals SR [1] and SR [2] are shown to be turned on two more times, but the invention is not limited thereto, and the reset scan signal is transmitted after the signal is transmitted to the data line. Additionally, the level may be at least one more time. For example, the reset scan signal may be periodically turned on after a signal is transmitted to the data line.

In order to generate the reset scan signal shown in FIG. 8, the gate driving circuit may use a start pulse signal that is turned on at least once more during one frame period or periodically turned on.

In another embodiment illustrated in FIG. 7, signals that are not actually read are accumulated in the capacitor C1 during a period (T57-T58) from a time when the scan signal is turned off level to a time when the next reset scan signal is turned on. do. When a leakage current is generated through the transistor T2, the data line may be affected, thereby affecting a signal read through the data line.

In particular, as the amount of light to be recognized decreases and the exposure time decreases, the periods T57-T58 become longer, and the signal accumulated in the capacitor C1 becomes stronger, and the possibility of leakage current through the transistor T2 increases. Then, interference may occur between sensor pixels sharing the data line.

In another embodiment illustrated in FIG. 8, the reset scan signals are additionally turned on to reset the signal accumulated in the capacitor C1, thereby preventing the above problem. However, when the reset scan signal is periodically turned on, coupling occurs between the reset gate line and the crossing data line, which may affect a signal transmitted through the data line.

9 is a view showing a waveform of a reset scan signal according to another embodiment.

As shown in FIG. 9, the reset scan signal is turned off only in a predetermined section during one frame period.

For example, at the time point T91, the reset scan signal SR [1] of the on level falls to the low level which is the off level. At time T95, the scan signal S [1] is turned on, and the exposure time of the first sensor pixel row is controlled by T91-T95. Subsequently, at time T93, the reset scan signal SR [2] of the on level falls to the low level which is the off level. At time T96, the scan signal S [1] is turned on, and the exposure time of the first sensor pixel row is controlled by T93-T96.

According to the above method, the sensor pixel does not have a signal that will not be read for a long time, and the leakage current through the transistor T2 is rapidly reduced. In addition, the influence of coupling between the data line and the reset gate line can be prevented.

1: sensor
10: sensor panel
20: gate driving circuit
30: sensing readout circuit
40: reset voltage generation circuit
50: photosensitive circuit
60: bias voltage generation circuit
70: light source

Claims (15)

Multiple data lines,
A plurality of scan lines through which a plurality of scan signals are transmitted,
A plurality of reset scan lines to which a plurality of reset scan signals are transmitted, and
A sensor that is reset by a reset voltage transmitted in synchronization with a corresponding reset scan signal, generates a pixel voltage according to light supplied during an exposure period, and transmits the pixel voltage to a corresponding data line in synchronization with a corresponding scan signal A sensor panel including a plurality of pixels,
The exposure period is a period from a time when the corresponding reset scan signal is changed to an off level to a time when the corresponding scan signal is changed to an on level, a fingerprint and an image sensor. According to claim 1,
The corresponding reset scan signal has a predetermined phase difference in the same waveform as the corresponding scan signal, fingerprint and image sensor. According to claim 1,
The corresponding reset scan signal has an on level at least twice during a period of one frame,
The exposure period,
Fingerprint and image sensor, which is a period from the time when the corresponding reset scan signal is changed from one on level to the off level of at least two times, and when the corresponding scan signal is changed to on level. According to claim 3,
The corresponding reset scan signal periodically has an on level after a point in time during which the corresponding scan signal is changed from an on level to an off level during the one frame period. According to claim 1,
The corresponding reset scan signal is off level for a predetermined period of one frame period,
The exposure period,
Fingerprint and image sensor, which is a period from a time when the corresponding reset scan signal is changed from an on level to an off level to a time when the corresponding scan signal is changed to an on level. In the sensor pixel to generate a pixel voltage according to the supplied light,
A photodiode connected between the first contact and the bias voltage,
Capacitance capacitor connected in parallel to the photodiode,
A reset transistor supplying a reset voltage to the first contact according to the reset scan signal, and
And a switching transistor that delivers the pixel voltage, which is the voltage of the first contact, to the data line according to the scan signal,
The sensor pixel accumulates a signal in the capacitor during an exposure period from a time when the reset scan signal is changed to an off level to a time when the scan signal is changed to an on level. The method of claim 6,
The reset scan signal has the same waveform as the scan signal, and has a predetermined phase difference. The method of claim 6,
The reset scan signal has an on level at least twice during one frame period,
The exposure period,
A sensor pixel, which is a period from a time when the reset scan signal is changed from one on level to an off level of the at least two times, and a time when the scan signal is changed to an on level. The method of claim 8,
The reset scan signal has a sensor level periodically after a point in time during which the scan signal is changed from an on level to an off level during the one frame period. The method of claim 6,
The reset scan signal is off level for a predetermined period of one frame period,
The exposure period,
A sensor pixel, which is a period from a time when the reset scan signal changes from an on level to an off level to a time when the scan signal changes to an on level. In the driving method of the fingerprint and image sensor comprising a plurality of sensor pixels,
Transmitting a plurality of reset scan signals to each of the plurality of sensor pixels,
Transmitting a plurality of scan signals to each of the plurality of sensor pixels,
During an exposure period from a time when each of the plurality of reset scan signals is changed to an off level to a time when each of the plurality of scan signals is changed to an on level, a plurality of pixel voltages are applied according to light supplied from the plurality of sensor pixels. Generating steps, and
And transmitting the plurality of pixel voltages to a plurality of data lines in synchronization with on-levels of the plurality of scan signals, respectively. The method of claim 11,
Each of the plurality of reset scan signals,
A method of driving a fingerprint and an image sensor having a predetermined phase difference in the same waveform as a corresponding scan signal among the plurality of scan signals. The method of claim 11,
Each of the plurality of reset scan signals,
Have a level that came at least twice in one frame period,
The exposure period,
A method of driving a fingerprint and an image sensor, which is a period from a time when each of the plurality of reset scan signals is changed from one on level to an off level of at least two times, and a time when the scan signal is changed to an on level. The method of claim 13,
Each of the plurality of reset scan signals, during the one frame period, periodically has an on level after a point in time when a corresponding scan signal among the plurality of scan signals is changed from an on level to an off level. . The method of claim 11,
Each of the plurality of reset scan signals is off level for a predetermined period of one frame period,
The exposure period,
A method of driving a fingerprint and an image sensor, which is a period from a time when each of the plurality of reset scan signals changes from an on level to an off level to a time when the scan signal changes to an on level.

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